Explainer - Why can't Israel keep a government together?

The coalitions change but one constant remains: debate about whether Israel should continue to be led by Benjamin Netanyahu, who has been prime minister for nearly a fifth of the country's 72-year-history.

The veteran right-winger universally known as "Bibi" is the dominant political figure of his generation. So why is he unable to hold a government together?

BUDGET

The immediate cause was arguments over the budget - failure to pass a fiscal package by midnight on Tuesday automatically forced a poll, to be held on March 23.

A budget was key to implementing a deal in which Netanyahu, 71, was to have handed power in November to his main rival, centrist former general Benny Gantz, switching places as "alternate prime minister."

WEAK COALITION

Gantz went from opposition leader to Netanyahu coalition partner after agreeing to form a unity government last May. He argued a power-sharing deal was in the national interest after three inconclusive elections had left the country paralysed.

But Gantz's followers were furious, his party split and Netanyahu believed his Likud Party would benefit, picking up seats.

Instead, Netanyahu's own party suffered a defection earlier this month. Gideon Saar, 52, shares many of Netanyahu's right- wing views but said Likud had become a "personality cult."

An opinion poll on Israel's Kan public TV on Tuesday showed Saar was drawing even with Netanyahu in popularity ratings.

"CRIME MINISTER"

In May, Netanyahu became the first serving Israeli prime minister to go on trial, appearing in court on charges of bribery, fraud and breach of trust.

The indictment alleges that he received gifts from millionaire friends and sought regulatory favours for media tycoons in return for favourable coverage.

Netanyahu denies all wrongdoing and his Likud Party faithful have stayed loyal, accepting his claim to be the victim of a political witch hunt.

But he faces a series of hearings in the New Year, and protesters have refused to let the issue fade away, staging demonstrations outside his Jerusalem residence with banners saying "Crime Minister".

Critics believe Netanyahu only agreed to the deal with Gantz because he hoped the "alternate" premiership would stop him having to resign under rules that allow a prime minister to remain in office even if charged with a crime.

COVID-19

Although Netanyahu gained plaudits for his early handling of the coronavirus pandemic in the spring and has secured vaccinations for Israelis, public anger has flared amid a series of national lockdowns and economic hardship for business owners.